Communication systems for business and personal use that transmit data to one or multiple receivers at very high rates of speed, e.g., up to tens of GHz, with improved spectral efficiency are desirable. A popular wireless access technology used for digital modulation and encoding for high-speed data transmissions to multiple receivers is Orthogonal Frequency-Division Multiple Access (OFDMA). Multiple access is achieved in OFDMA by assigning, to multiple users, subsets of frequency subcarriers associated with a broadband wireless channel. However, the ability of current wireless access technologies, including OFDMA, to achieve high data throughputs with low block-error rates can be restricted by frequency selective fading due to multipath propagation between a transmitter and multiple receivers, multi-user interference, and frequency offset between the transmitter and receivers.
Embodiments of the present disclosure are illustrated by way of example and are not limited by the accompanying figures. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some elements in the figures may be exaggerated relative to other elements to help to improve understanding of the embodiments.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings. Some drawings show only those specific details that are pertinent to understanding the embodiments, so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Also, the functions included in any flow diagrams do not imply a required order of performing the functionality contained therein.